Salvage pontoon



1 A. l. BRUNO I 2,870,730

' SALVAGE PONTOON Filed Feb. 1, 1956 2 Sheets-Sheet 1 INVENTOR ANTHONYI. BRUNO ATTORNEYS A. l. BRUNO SALVAGE PONTOON Jan. 27, 1959 2Sheets-Sheet 2 Filed Feb. 1, 1956 INVENTOR ANTHONY l. BRUNO BY f v /aATTORNEYS Unite This invention relates to salvage pontoons for raisingsunken crafts and other objects, and is more particularly concerned withpontoons in the form of bags or balloons and constructed of flexiblematerial so that they may be completely collapsed when deflated.

In order to avoid the formation within the unit of excessive pressuresgenerated by the decrease of external pressure on the unit as it rises,pontoons of the indicated type have heretofore been made either withnormally closed outlet ports controlled by suitable means, such as,mechanical safety valves, or with open bottoms to permit free escape ofthe inflating medium under increased internal pressures. The methodsheretofore devised for controlling the pressures on the normally closedtype of pontoon have proved unsatisfactory because of the time elementinvolved in discharging the necessary amount of air through a smallopening to compensate for the decreased external pressure, and becausethe speed of rise of the pontoon might vary instantly. As a result ofthese conditions, the pressures within the unit are usually irregularand out of balance with the external pressures, and there is the dangerthat the internal pressures will vary so rapidly relative to theexternal pressures as to cause sudden excessive stresses on the liftingtackle, the parting or sudden snapping of the pontoon from its anchor,and eventual rupture of the pontoon itself.

While the pontoons which were provided with open bottoms avoided theabove discussed disadvantages of the normally closed pontoon, theypossessed other disadvantages that rendered them impractical forsalvaging operations. is under water, any movement or pressure on thebag tending to tilt it from its true vertical axis, such as may occurfor example, from the bag bumping against the side of a ship, or becauseof the form of the ship at the place where the bag is attached thereto,or from tides or currents, etc., will enable the air in the bag toinstantly escape through the so inclined bottom opening-thereof which isof relatively large area. This sudden escape of the air destroys thepressure balance on the bag and the external pressure, which is nowgreater than the internal pressure, will tend to force the remainder ofthe inflating medium from the interior of the bag. As the bag isdeprived of its buoyant medium it will be caused to sink inert towardsthe sea bottom. When conditions are such that an open bag or envelope isenabled to rise to the surface of the sea, it will, because of itsextremely buoyant condition, be subject to movement by sea swells,waves, tides or current, which if sufficiently strong will cause the bagto move from side to side in pendulous fashion.

Here again as the bag is swung from its true vertical axis or position,the inclined open bottom will enable the air to escape thus renderingthe pontoon incapable of maintaining the raised object afloat. Thisdanger also exists when it is necessary to tow the raised craft eitherto drydock, or some other destination, since the movement of thepontoons against the water will cause the resisting pressure of thelatter to tilt the pontoons thus causing a Thus, when an open bottom bagor envelope States Patent displacement of the bags from the truevertical axis or position and a consequent loss of the buoyant orinflating medium from within their interiors. It will thus be seen thatin order that the open bottom pontoon be used successfully it mustretain its true vertical axis or position at all times, anaccomplishment which this type of bag is unlikely to perform because theideal conditions necessary to that end are seldom enjoyed at sea and ifso not for any great length of time.

The primary purpose of the present invention is to provide a pontoonwhich is free of the above discussed disadvantages of prior pontoons,and which is so constructed that it will provide a practical, efiicientand safe means for salvaging sunken objects throughout the entireperiods of such operations from the time the unit is attached to theobject to be raised, until the latter is safely drydocked or towed toother ultimate destination.

A further object of the invention is to provide an improved salvagepontoon which will be substantially unaffected in its operability by seaconditions or currents during the raising and supporting operations andwhich can be safely moved through the water at the speed of towing forsubstantial periods with great maneuverability and without danger of anyloss of buoyancy.-

Another object of the invention is to provide an improved pontoon thatcan be safely raised without damage through the water and which when itreaches the surface can be made substantially unsinkable.

A still further object of the invention is to provide an improvedpontoon which is capable of maintaining afloat a weight substantiallygreater ,than the weight it was capable of raising from the sea bed.

Other objectsas well as the advantages and novel de- A tails ofconstruction of my improved pontoon, will become apparent from a perusalof the following description when read in connection with theaccompanying drawings, which illustrate one method of carrying out theinvention and in which:

Fig. 1 is a schematic view showing a pontoon of this invention attachedto an object on the sea bottom and prior to the supply of an inflatingmedium to the pontoon;

Figs. 2 to 4 are views similar to Fig. 1, but show respectively, theappearance of the pontoon when an inflating medium has been suppliedthereto, the manner in which pressures on the pontoon are balancedduring the lifting of the object, and the arrangement of the partsthereof after the pontoon has reached the surface and been operated tosupport the object in such position;

Fig. 5 is an elevational view, partly in section, to show the details ofconstruction of the pontoon;

Fig. 6 is a top plan view of the pontoon shown in Fig. 5;

Pi g. 7 is a bottom view of the bag of the pontoon shown in Fig. 5 andindicates in dotted outline the opening of the bottom wall thereof toequalize pressures on such bag during the rise thereof, as illustratedin Fig. 3; and

Fig. 8 is a vertical sectional view of the valve mechanisms forinflating the bag during its rise from the sea bottom and after it hasreached the surface of the ocean.

In the drawings the inflatable bag or envelope of the pontoon isindicated generally by the reference numeral 10. This bag may be made ofany suitable'light weighted, flexible, non-porous material capable ofwithstanding the ravages of salt water,-such as for example, a lightsailing or marine canvas, treated with a suitable primer and then coatedwith natural or synthetic rubber, or a rubber coated fabric made ofsynthetic material. The bag 10 may have any desired shape suitable forthe pur poses intended, but it is preferred to make it of generallycylindrical form, as shown in the drawings. The bag illustrated iscomposed of a plurality of layers 11 of rubber coated canvas to give "itthe necessary strength for-salvaging operations? The-layers '11 areformed to i provide a cylindrically shaped body 12 and a top wall 13which joins the body 12 ina smooth curve, as is shown more clearlyinFig. 1=of-the drawings. At the-center of the top wall 13 is securedan-eye bolt 14 to which is connected the cable 15 by which the pontoonis lowered in' a deflated condition from a ship or operational pon toonto the object to be raised. The eye bolt 14-has a shank which extendsthrough top Wall '13, and is suitably connected to the material of suchtop wall by appropriate washers and lock nuts known to the art whichenable an air tight connection to be made and without danger of damageto the material of the wall in the use of the pontoon; Secured to theshank of eye bolt id as by means of'welded ,bars16 is-a circular ring 17which rests on the outersurface of the top wall 13. The ring 17serves'as a means for anchoring the upper ends of a'plurality ofcables18, which extend radially'outwardly from such ring, over the curvedjuncture of top wall 13 and cylindrical'body 12, and then verticallydown to a ring 19 located in adjacent spaced relation below the bottomend of the body 12. Each cable 18 is preferably a steel cable coveredwith or contained within a tube of plastic material in order to minimizeas much as possible any damage which might be caused'by such cables tothe material of top wall 13 and body12 of the bag during the rising andtowing operations. The upper ends of the cables 18' are looped aroundand permanently connected to ring 17 by suitable fasteners known to theart. In a similar fashion the lower ends of cables 18 are secured toring 19. It willbe noted from Fig. 5 of the drawings, that ring 19,which may be located about one foot below the bottom end of thebag body12, is provided on its inner and outer peripheral edges with a pluralityof aligned, inner and outer recesses or notches .20 and 21,respectively, Each pair of notches 2 21 are spaced from adjacent pairsof such notches and receive the lower looped end of a cable 18. Thedepth of the notches may be such that the looped end of the cables willbe flush with or in back of the inner and outer peripheral surfaces ofthe ring 19.

The cables 18 at the bottom end of the bag body pass inwardly throughgrommets 22 provided around such bottom end. Secured to each cable aboveits associated grommet 22, is a non-slip nut 23 having an outsidediameter greater than the diameter of the opening in the grommetso thatit functions as a stop to prevent the bag from sliding upward on thecables 18 when inflated and rising It will thus be seen that cables 18,ring 19, grommets 22 and stops 23 coact to maintain these parts togetherwith the bottom end of the bag body substantially in their assembledrelation during the use of the pontoon, and to maintain the cylindricalconfiguration of the bag at its lower end. Inasmuch as the ring 19 is ofa fixed diameter, substantially the same as the diameter of the bag body12, the bottom section of thebag will be caused bysuch partsto have afixed circumference especially when'the bag is provided with theinflating medium: The cylindrical shape of the bag is also maintainedbythe cables 18 and a plurality of circular, verticallyspaced cables 24arranged on the exterior surfaces of the bag body 12 and top wall 13 andsimilar in construction to cables 18. As indicated in the drawings, thecables 18 and 24 are maintained in their proper relation on the bag,while permitting movement relative to each other, by a plurality ofpatches 25 and strips 26-;of material similar to the bag material andcemented securelyto the latter without binding the cables to eitherso'that they may move relatively freely thereto. As the cables at theircrossings are unconnected it will be understood that while the bag isconfined within the network formed thereby, the cables in the networkmay have relative movement subject to the confining influiii ence of thepatches 25 and strips 26. Preferably the cables 18-overlie-thecables 24so that when the. bagsis inflated the former will hold the lattersecurely in their proper positions. Preferably also, there are provideda sufiicient number of cables 18 and cables 24 on the upper wall 13(note Fig. 6) so that together with the latter there is provided at thetop of the bag a strong wall capable of resisting relativelyhighinternal pressures on the bag during its ascension and in effect forcingthe gas when under such high pressures to escape through the bottom ofthe bag, as will hereinafterbe more fully explained. The upper end ofthe bag during its raising operations is also strengthened by an innerwall 30 which shall now be described.

The inner wall 30 is constituted of one or more layers of materialsimilar to that forming the exterior walls 12 and 13 of the bag so as toprovide a light, flexible, non-porous wall having relatively greatstrength. As the inner wall, during the descending and raisingoperations of the pontoon, lines the upper portion of the bag 10, as isshown in Figs. 1 to 3 and 5,. it has a shape conforming to that of suchportion of the bag. In other words, the inner wall 30 has acylindrically shaped body portion similar to the upper part of the bagbody 12, and a top portion similar to the top wall 13 of the bag. Thebottom circular edge portion 31 of 'wall 3! is folded up and permanentlysecured by a suitable bonding material of known make capable of makingan air-tight connection between the two walls; By reason of this mannerof connecting wall 3010 the bag 10, the former may be readily turnedinside out so'that it depends from its line of juncture with the bagbody 12 to form with the upper part of bag 10 anair-tight cylindricallyshaped chamber, as shown in Fig. 4. The length of the cylindricallyshaped body portion of wall 30 is greater than the length of bag 10 fromthe line of juncture of such bagwith wall 3% to the bottom end of suchbag, so that the cubic area of such chamber'is substantially greaterthan'the cubic area of the bag 16 when the latter is in a fully inflatedcondition.

When the'wall 31 is folded upwardly in the manner shown in Figs. 1 to 3and 5, so that it forms the inner wall of the upper part of bag 10, itis maintained insuch position by the valve means by which the inflatingmedium is supplied to the chamber in such bag partly defined by suchinner wall. As is shown more clearly in-Fig; 8 of the drawings, suchvalve means includes an internal air valve composed of a valve casing 32which is secured to the edge of a circular opening in the wall 30 in'aknown manner toform an airtight connection. The valve casing 32 has aninlet opening'33 which is closed by a valve member 34, and a permanentlyopen'discharge opening 35. The valve member 34 is biased to closedposition by a coiled spring 36 of such strength that it 'is capable ofmaintaining the opening 33 closed against pressures greater than thatthat can safely be supplied to the bag 10 when the wall 30 is in alowered position as shown in Fig. 4. The Valve member 34 is retractedfrom the position shown in Fig. 8, by a tube 37 which threadedly en "Egages the edge of opening 33 and may be advancedtoa position where thetransverse passages 38 in the lower end thereof bring the interior ofthe tube into communication with the interior chamber of the valvecasing 32. The threaded fitting between the casing 32 and tube 37 is soclose that it is substantially air-tight and all of the inflating mediumsupplied through tube 37 will pass through the casing 32 and out theopening 35 thereof into the interior of the bag 10. The tube 37 extendsin threaded engagement through a fitting 39 secured to the edge of acircular opening, in the top wall 13 of the bag 10 in a known manner toform an air-tight connection. Like the. valve casing 32, the threadedengagementbetween fitting 39 and tube 37 is so close that it isair-tight and will not leak air or gas under pressures supplied to thebag when the wall 30'is in a lowered position'as shown It will beunderstood from the foregoing that when the inner wall is foldedupwardly in the manner of Figs. 1 to 3 and 5, the valve casing 32 willcome into alignment with the fitting 39 to enable the tube 37 to bereadily brought into threaded engagement with the sides of the casingopening 33. The tube 37 is rotatably advanced until the valve member 34is moved to a retracted position such that the passages 38 come intocommunication with the interior of the casing and thereby enable theinflating medium to be supplied to the interior of the bag 10. Thisfolding of the inner wall 36 and the connection thereof to the top wall13 of the bag by the aforesaid valve means is preferably done onboardthe tender prior to preparing the bag to be lowered to the sea bottom.The parts remain in this condition during the raising of the object fromthe sea bottom. When the bag reaches the surface of the water afterhaving raised the object, crew members in rowboats can readily turn thenutlike portion 40 of the tube 37 to unscrew the tube from the valvecasing 32, thereby permitting the valve member 34 to close opening 33,and releasing the inner wall 30 from the top wall 13 of the bag. Whenair is caused to flow again, it will be fed by the tube 37 between theinner wall 30 and the top wall 13 of the bag thus causing wall 30 to beforced downwardly to assume the position shown in Fig. 4 and forcing theair out of the bag in a manner which shall be hereinafter explained.

The lower end of the body portion 12 of the bag is provided with abottom closure which is closed when the pressure of the inflating mediumwithin the bag balances the exterior pressures exerted on the bag by thewater during the raising operation, and which immediately andautomatically opens to restore such balance of pressures as soon as thepressure of the inflating medium rises above that of the surroundingwater on the bag during the raising operations. As shown more clearly inFigs. 5 and 7, this bottom closure is composed of two quadrisphericalsections 45, 46, the horizontal curved edges of WhlCh are secured in anair-tight connection to the interior surface of the bottom edge portionof the bag body 12, and the transverse curved edges of which are inoverlapping relation. In the construction shown, the transverse edgeportion of section 45 is outside the transverse edge portion of section46. The sections 45 and 46 are made of a resilient material such asnatural or synthetic rubber so that when internal forces within the bagtending to separate such transverse edges thereof, as indicated by thedotted lines in Fig. 7, to provide a transverse opening in the shape ofa spherical segment, no longer bear on such sections, the latter shallbecause of their inherent resiliency automatically return to the closedoverlapping position shown in Figs. 1, 2, 5 and 7. Preferably thesections 45 and 46 at their junctures with the bag 10 are thickest andthen taper gradually toward the middle of the transverse, overlappingedge portions thereof so that they automatically tend to open first atthe center of the closed wall formed thereby under pressure from theinflating medium. In the closed, overlapped COHCliLlOH of the sections45 and 46 they are relatively air-tight to a predetermined balancedpressure within the bag 10 because of the elastic qualities thereof.This quality as well as the opening and closing operations of thesections are enhanced by providing further resilient means tendingnormally to maintain the sections in closed position and to yieldinglyresist, without preventing, sudden opening of such sections underincreased internal pressures. As shown more clearly in Figs. 5 and 7,such means include a plurality of spaced elastic, rubber bands 47connected at one end to the transverse edge of section 45 and extendingover the outer surface 6 of section 46 to the line of juncture of thelatter section with the bag body 12. The other ends of the bands 47 arepreferably bonded between the horizontal edge of section 46 and thematerial of bag body 12. In a similar fashion rubber bands 48 areconnected at one end to the transverse edge of section 46, extend overthe outer surface of section 45, and are secured at their other endsbetween the horizontal edge of section 45 and the material of bag body12. Due to the fact that the transverse edge of section 46 is inside thetransverse edge of section 45, the connection of bands 48 to section 46is in back of the edge portion thereof overlapped by section 45 (noteFig. 5). When the bag is not under pressure the closed, semi-sphericallyshaped, wall formed by sections 45 and 46 will extend through ring 15,but will not engage the interior surface of such ring. However, when thebag 10 is inflated to raise an object from the sea bottom, suchsemi-spherically shaped wall will expand outwardly until it comes intorelatively tight engagement with the interior of ring 19 so that thelatter will tend to confine the chord of the opening of sections 45 and46 to the length of. the inside diameter of such ring.

It is believed that it will be apparent from the foregoing description,that prior to the lowering of the pontoon to the object to be raised,the inner wall 30 will be folded upwardly, as shown in Fig. 5, andconnected to the top wall 13 of the bag by the valve fittings, so thatit will in elfect constitute an inner strengthening wall for the upperpart of bag 10.

With the inner wall 30 so connected, the valve fit tings will be enabledto supply compressed air through the walls 13 and 30 of the bag into thechamber defined by inner wall 30, the lower part of bag body 12 and thebottom wall formed by sections 45, 46. The bag or balloon is lowered tothe object to be raised in a deflated state by the cable 15 connected tothe eye bolt 14. The coupling 49 suspended from the ring 19 by cables 50and the hook which i connected to such coupling will have a combinedweight suflicient to sink the pontoon even though there is some air inthe deflated bag 10. When the pontoon reaches the ocean bottom it may beconnected to the object to be raised in the manner shown in Fig. 1 ofthe drawings. An inflating medium, such as air, is then pumped into thebag 10 until the pontoon is buoyant enough to raise the object from thesea bottom (note Fig. 2). As the pontoon rises from the sea bottom, thelessening pressure of the surrounding water will cause the air withinthe bag to expand and increase in pressure. As soon as these internaland external pressures reach an imbalance sufficient to retract thesections 45 and 46, these sections will move automatically to provide awide enough opening capable of immediately discharging a bubble oramount of air sullicient to at once restore the balance of internal andexternal pressures (note Fig. 3). It will be understood that until thisimbalance is reached the sections 45 and 46 will remain closed toprevent any escape of air, but as soon as such imbalance is attainedsuch sections will open an amount proportional to the amount ofimbalance created. Since the sections 45, 46 are weakest in the centerof the closure wall formed thereby, the initial opening will be formedfrom a small slit in the center of such wall and will then increase intransverse directions under increased pressures until the length of theopening is equivalent to a chord having a length at least equal to theinterior diameter of the ring 19 and such opening is capable of enablingalmost the entire volume of the inflatable medium to escapeinstantaneously therethrough. Because of this construction, suddenstresses on the bag and lifting tackle are eliminated and the pressuresare maintained in substantial equilibrium throughout the rise of thebag. As the bag only opens in response to an imbalance of stresses andthroughout the remainder of the period of rise is in closed condition sothat no air can escape, it does not effect the buoyancy of the pontoonif it should be tilted from its true vertical axis in the liftingoperation.

When the pontoon reaches the surface of the ocean, the inner wall 30'isdisconnected in the manner previously described and compressed air isforced into the bag between such' inner wall and the bag. The force ofthis air will cause the inner wall 30 to move downward forcing outthrough the section Hand 46 the air thatwas used to lift the object fromthe sea bottom. When the chamber now defined at its lower end by theinner wall 30, is fully inflated, the parts will be. arranged as shownin .Fig. 4 of the drawings. The chamber so formed will provide aperfectly sealed pontoon capable of containing a greater volume of airthan the bag was capable of holding when arranged for the. liftingoperation and therefore capable of sustaining afloat a greater weightthan the pontoon lifted. It will be evident also that in this condition,the pontoon cannot be capsized or sunk by sea turbulence, tides orcurrents, and may be readily towed with entire safety. Provided in thetop wall 13 of the bag is a suitable safety valve 43 of knownconstruction capable of relieving the pressure of the air in the sealedpontoon defined at its lower end by the wall 30, when such pressure atany time is in danger of increasing to a point at which the pontoonmight be ruptured. The inner end of the safety valve is preferablyformed to minimize possible damage to wall Stlwhen it is folded upwardlyagainst the top bag wall 13.

While I have heretofore described and illustrated a preferred embodimentof my invention, it will be apparent to those skilled in the art thatvarious changes and modifications may be made Without departing from thespirit of the invention or the scope of the appended claims.

I claim:

1. A salvage pontoon comprising an envelope made of flexible,substantially non-stretchable material adapted to contain an inflatingmedium provided with an opening for escape of the inflating medium, anda wall composed of flexible, resilient material normally closing thearea of said opening, said wall having its peripheral edge portionssecured to said envelope around the edge of said opening and havingwithin the area defined by said secured edge portions thereofcooperative edge portions providing a vent opening under pressuredirectly applied by the inflating medium in said envelope, saidcooperative edge portions being normally closed by the inherentresiliency of said wall material when the internal and externalpressures on said envelope are substantially in balance to preventescape of the inflating medium therebetween and being automaticallyoperable as soon as there occurs a condition of unbalance in theinternal and external pressures on said envelope suflicient to overcomethe inherent resiliency of said wall to instantly release sufficient ofthe inflating medium to promptly restore a balanced condition of suchpressures.

2. A salvage pontoon for raising a submerged object comprising anenvelope made of flexible material adapted to contain an inflatingmedium, said envelope having a closed upper part and being provided atits lower part with an opening for escape of the inflating medium, aninner wall joined at its periphery to the inner wall of said envelopealong a line between the closed upper part and opening thereof and beingconfigured to be foldable up against the upper part of said envelopeduring the object raising operation and to be foldable downwardly toform with the upper part of said envelope a completely sealed pontoon,means for supplying inflating medium to said envelope when said innerwall is folded upwardly, said envelope supplying means being connectedto said envelope and affording communication to the chamber defined bysaid envelope and upwardly folded inner wall, and means connected tosaid envelope and communicating a; with the, space between said envelopeand said inner wall above the line of juncture of said inner wall withsaid envelope for supplying inflating medium to the'sealed pontoonformed by said envelope and inner Wall.

3. Asalvage pontoon comprising an envelope made of flexible,substantially non-stretchable material adapted to contain an inflatingmedium provided with an opening at its bottom for escape of theinflating medium, a rigid ring located exteriorly of and below saidenvelope and spaced adjacently below such opening thereof, a networkmounted on and within which the envelope is confined for supporting saidring in suspended relation below said envelope, said network and ringcoacting to maintain the edge portion of said material forming suchopening in theconfiguration of said ring, and a wall composed offlexible, resilient material normally closing the area of said openingand normally spaced inwardly from said ring,'said wall having itsperipheral edge portions secured around the edge of said opening andbeing expandable downwardly and outwardly towards said ring underpressure directly applied by the inflating medium in said envelope, saidwall having within the areas defined by such secured edge portionsthereof and said ring cooperative edge portions providing a vent openingunder such pressure, said'cooperative edge portions being normallyclosed by the inherent resiliency of said wall material when theinternal and external pressures on said envelope are substantially inbalance to prevent escape of the inflating medium therebetween and beingautomatically operable as soc-n as there occurs a condition of unbalancein the internal and external pressures on said envelope suflicient toovercome the inherent resiliency of said wall to instantly releasesuflicient of the inflating medium to promptly restore a balancedcondition of such pressures, and said ring through its engagement bysaid wall limiting the size of the opening for release of the inflatingmedium.

4. A salvage pontoon comprising an envelope made of flexible,substantially non-stretchable material adapted to contain an inflatingmedium provided with an opening for escape of the inflating medium, anda wall composed of flexible, resilient material norm-ally closing theareaiof said opening and automatically operable as soon as .there occursa condition of unbalance in the internaland external pressures on saidenvelope to instantly release suflicient of the inflating medium topromptly restore a balanced condition of such pressures, said wallcomprising a plurality of sections secured in air-tight condition attheir'outer peripheral edge portions to the edge portion of saidmaterial forming such opening and having transverse edge portionsarranged in overlapping relation, the resilient material of which suchsections are constituted normally maintaining such transverse edgeportions in closed overlapping relation and yieldingly resistingmovement of such transverse edge portions away from such overlappingrelation.

5. A salvage pontoon comprising an envelope made of flexible,substantially non-stretchable material adapted to contain an inflatingmedium provided with anopening for escape of the inflating medium, and awall composed of flexible, resilient material normally closing theareaofsaid opening and automatically operable as soon as there occurs acondition of unbalance in the internal and external pressures on saidenvelope to instantly. release suflicient of the inflating medium topromptly restore a balanced condition of such pressures, said wall beingcomposed of rubber material and gradually diminishing in thickness fromthe edge portion of said material forming such opening to the centralpart of said wall, and a transversely extending normally closed openingprovided in said wall and extending into the central portion thereof.

6. A salvage pontoon comprising an envelopemade of flexible,substantially non-stretchable material adapted to contain an inflatingmedium provided with an opening for escape of the inflating medium, anda wall composed or flexible, resilient material normally closing thearea of said opening and automatically operable as soon as there occursa condition of unbalance in the internal and external pressures on saidenvelope to instantly release suflicient of the inflating medium topromptly restore a balanced condition of such pressures, said wallcomprising a plurality of sections secured in air-tight condition attheir outer peripheral edge portions to the edge portion of saidmaterial forming such opening and having transverse edge portionsarranged in overlapping relation, and means carried by said envelope andconnected to said transverse edge portions and constructed and arrangedto maintain such transverse edge portions in closed overlapping relationand to yieldingly resist movement of such transverse edge portions awayfrom such overlapping relation.

7. A salvage pontoon comprising an envelope made of flexible,substantially non-stretchable material adapted to contain an inflatingmedium provided with an opening for escape of the inflating medium, anda wall composed of flexible, resilient material normally closing thearea of said opening and automatically operable as soon as there occursa condition of unbalance in the internal and external pressures on saidenvelope to instantly release sufficient of the inflating medium topromptly restore a balanced condition of such pressures, said wallcom-prising a plurality of sections secured in air-tight condition attheir outer peripheral edge portions to the edge portion of saidmaterial forming such opening and having transverse edge portionsarranged in overlapping relation, and means for maintaining suchtransverse edge portions in closed overlapping relation and yieldinglyresisting movement of such transverse edge portions away from suchoverlapping relation, said last mentioned means including a plurality ofstretchable bands secured to the transverse edge portion of each sectionand extending over the outer surface of another section, the outer endsof such bands being secured to the edge portion of said material formingsuch opening.

8. A salvage pontoon comprising an envelope made of flexible,substantially non-stretchable material adapted to contain an inflatingmedium provided with an opening for escape of the inflating medium, anda wall composed of flexible, resilient material normally closing thearea of said opening and automatically operable as soon as there occursa condition of unbalance in the internal and external pressures on saidenvelope to instantly release suflicient of the inflating medium topromptly restore a balanced condition of such pressures, said wallcomprising a pair of quadrispherically shaped sections secured inair-tight condition at their outer peripheral edge portions to the edgeportion of said material forming such opening and having a transverseedge portions arranged in overlapping relation, and a plurality ofrubber bands connected to such transverse edge portions and to such edgeportion of said material and normally tending to maintain suchtransverse edge portions in closed, overlapping relation.

9. A salvage pontoon for raising a submerged object comprising anenvelope made of flexible material adapted to contain an inflatingmedium provided with an opening for escape of the inflating medium, aninner wall joined at its periphery to the inner wall of said envelopeand foldable up against the upper part of said envelope during theobject raising operation and foldable downwardly to form with the upperpart of said envelope a completely sealed pontoon, said inner Wallhaving a length greater than the length of said envelope from the lineof juncture of said inner Wall therewith, to the edge portion of theenvelope material forming said opening, and such sealed pontoon having asubstantially greater capacity for the inflating medium than saidenvelope, means for supply ing inflating medium to said envelope whensaid inner wall is folded upwardly, said envelope supplying means beingconnected to said envelope and affording communication to the chamberdefined by said envelope and upwardly folded inner wall, and meansconnected to said envelope and communicating with the space between saidenvelope and said inner wall above such line of juncture for supplyinginflating medium to the sealed pontoon formed by said envelope and innerwall.

10. A salvage pontoon comprising an envelope made of flexible materialadapted to contain an inflating medium provided with an opening forescape of the inflating medium, an inner wall joined at its periphery tothe inner wall of said envelope and foldable up against the upper partof said envelope during the object raising operation and foldabledownwardly to form with the upper part of said envelope a completelysealed pontoon after raising such pontoon, valve means including anormally closed valve provided on said inner wall, a valve memberconnected to a source of supply of inflating medium and extendingthrough said envelope to enable it to feed such medium to the sealedpontoon formed by said envelope and inner wall, said valve member beingengageable with said valve to secure said inner wall to said envelopewhen the former is folded up against the top of the latter and toactuate said valve to enable inflating medium to be supplied from saidvalve member to said envelope when said inner wall is so secured.

11. A salvage pontoon comprising an envelope made of flexible-materialadapted to contain an inflating medium and having an upper part locatedabove an opening for escape of the inflating medium, closure meanscomposed of flexible, resilient material normally closing the area ofsaid opening and automatically operable as soon as there occurs aconditionof unbalance in the internal and external pressures on saidenvelope to instantly release suflicient of the inflating medium topromptly restore a balanced condition of such pressures, and an innerwall joined at its periphery to the inner wall of said envelope andfoldable upwardly to re-enforce such upper part of said envelope andfoldable downwardly to re-enforce said closure means.

References Cited in the file of this patent UNITED STATES PATENTS2,413,313 Cook Dec. 31, 1946 2,475,839 Jalbert July 12, 1949 2,492,800Isom Dec. 27, 1949 2,635,574 Sturtevant vApr. 21, 1953 FOREIGN PATENTS122,961 Germany Aug. 14, 1901

